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Biomedical subjects

S Kan

Publications and source records attributed to S Kan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Importance of thymus to maintain operational tolerance to fully allogeneic cardiac grafts.

BACKGROUND: The effectiveness of donor-specific blood transfusion (DST) before transplantation has been established. Anti-CD4 monoclonal antibody (anti-CD4) augments the ability of DST to induce indefinite prolongation. Therefore, we investigated the importance of thymus to maintain the unresponsiveness to alloantigens. METHODS: CBA mice were pretreated with 0.25 mL of DST or two doses of anti-CD4 before transplantation of a C57BL/10 heart. Some mice were thymectomized. RESULTS: Naive CBA mice rejected C57BL/10 grafts acutely with a median survival time of 7 days. When mice were pretreated with anti-CD4 plus DST 4 weeks before transplantation, all grafts survived indefinitely (>100 days), whereas mice treated with DST alone or anti-CD4 alone rejected acutely (median survival time, 7 and 12 days, respectively). To investigate the importance of thymus, mice pretreated with anti-CD4 plus DST 4 weeks before transplantation were thymectomized or underwent a sham operation 1 day before grafting. Mice with the sham operation accepted grafts indefinitely, whereas thymectomized mice rejected the majority of the grafts (median survival time, 20 days). CONCLUSIONS: The thymus is important in maintaining the operational tolerance induced by anti-CD4 plus DST 4 weeks before grafting.

Adoptive Transfer↗
PubMed2001

Clinical significance of tissue blood flow during esophagectomy by laser Doppler flowmetry.

OBJECTIVES: We sought to investigate the effect of tissue blood flow on the incidence of anastomotic leakage during esophagectomy. METHODS: Reconstruction was done with a gastric tube, and all cases involved cervical anastomosis. Tissue blood flow of 43 patients was measured with a laser Doppler flowmeter before emplacement and after anastomosis during surgical intervention. The reconstruction route and tissue blood flow before emplacement and that after anastomosis were analyzed as possible factors influencing anastomotic leakage. RESULTS: Tissue blood flow after anastomosis with leakage was 9.1 +/- 2.0 mL/min per 100 g, and that without leakage was 13.7 +/- 2.9 mL/min per 100 g. Tissue blood flow with leakage was significantly lower than that without leakage (P <.01, unpaired t test). Twenty-one patients had tissue blood flow after anastomosis of greater than 13 mL/min per 100 g, and none of them had leakage, whereas 5 patients had blood flow of less than 10 mL/min per 100 g, and all 5 had leakage. CONCLUSION: Tissue blood flow can be an important and useful indicator of the presence of current anastomotic leakage. Low tissue blood flow after anastomosis may mediate for appropriate surgical or pharmacologic interventions to detect, localize, and counteract leakage.

Anastomosis, Surgical↗
PubMed2001

Tight Sylvian cisterns associated with hyperdense areas mimicking subarachnoid hemorrhage on computed tomography--four case reports.

Four patients with supratentorial mass lesions (two chronic subdural hematomas, one acute epidural hematoma, and one acute subdural hematoma) showed hyperdense sylvian cisterns on computed tomography (CT). Association of subarachnoid hemorrhage was suspected initially, but was excluded by intraoperative observation or postoperative lumbar puncture. CT showed disappearance of the hyperdense areas just after evacuation of the mass lesions. The hyperdense areas are probably a result of the partial volume phenomenon or concentrations of calcium deposits rather than abnormally high hematocrit levels, which were not found in these patients.

Accidental Falls↗
PubMed2001

Rupture of pial arteriovenous malformation associated with early thrombosis of the draining system following stereotactic radiosurgery--case report.

A 50-year-old man was treated with stereotactic gamma knife radiosurgery for an incidentally detected small callosal arteriovenous malformation (AVM) with stenosis of the main draining pathway. He suffered two episodes of intraventricular hemorrhage at 4 and 14 weeks after the radiosurgery. Radiological studies demonstrated that the anterior portion of the draining system including a varix, which had been irradiated, was thrombosed before the obliteration of arteriovenous shunts. Stereotactic radiosurgery is an accepted treatment for selected small and medium AVMs, but this procedure may increase the risk of bleeding. Early occlusion of a part of the draining pathway after stereotactic radiosurgery might have induced AVM rupture. An impaired venous outlet, either consisting of one draining vein or with stenosis, present before treatment may be develop thrombosis in response to high-dose irradiation.

Aneurysm, Ruptured↗
PubMed2001

Coil embolization for the treatment of ruptured dissecting vertebral aneurysms.

BACKGROUND AND PURPOSE: Proximal occlusion of the parent artery has been widely used for treatment of vertebral dissecting ruptured aneurysms, but this does not always completely prevent rerupture. We retrospectively studied 24 consecutive patients for clinical characteristics and/or for efficacy of occlusion with detachable coils at the site of dissection. METHODS: During a 45-month period, 24 of 242 patients with aneurysms associated with subarachnoid hemorrhage had dissecting vertebral aneurysms identified at angiography. Eighteen of the 24 patients were treated with platinum coil occlusion at the affected site as early as possible after diagnosis, two patients were treated conservatively, and four others were not eligible for treatment owing to intractable elevation of intracerebral pressure and severe brain stem dysfunction. RESULTS: The rate of aneurysmal rupture in the posterior fossa was high, at 56 (23%) of the 242 aneurysms, including 24 (10%) vertebral dissecting aneurysms. Subsequent rupture occurred in 14 (58%) of the patients, all within 24 hours after the first attack and three during transportation to the hospital. In all 18 patients, coil embolization at the affected site was successful, with no complications. Radiologic findings showed complete occlusion of the dissection site and patency of the unaffected artery (mean follow-up, 9 months). Among the six patients who did not undergo embolization, only one survived with a good outcome, the others died of repeat hemorrhage. CONCLUSION: A high rate of vertebral artery dissecting aneurysms may be expected in patients with subarachnoid hemorrhage, especially in those with early repeat hemorrhage. Detachable platinum coil embolization may be more effective than proximal occlusion for treatment of ruptured vertebral dissecting aneurysms because of immediate cessation of blood flow to the dissection site; however, in patients with bilateral dissections or hypoplastic contralateral vertebral arteries, prior bypass surgery orstent placement to preserve the artery will be needed.

Adult↗
PubMed2000

Pathologic significance of tumor progression in locally recurrent rectal cancer: different nature from primary cancer.

PURPOSE: It has recently been demonstrated that the tumor growth rate is a stronger determinant of survival than the extent of the growth in local recurrence of rectal cancer. We studied which factors controlled the tumor growth rate using modern immunohistochemical methods. METHODS: In 51 patients who underwent extended resection for this condition, paraffin-embedded specimens were examined for 1) tumor angiogenesis by CD31 staining and microvessel counting, 2) apoptosis by terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling staining, and 3) cellular proliferative activity using anti-proliferative cell nuclear antigen antibody. The results were compared with carcinoembryonic antigen doubling time and survival. RESULTS: The five-year survival rate was 20 percent. The postoperative carcinoembryonic antigen doubling time, which was the strongest predictor of survival, correlated highly with proliferative cell nuclear antigen labeling index, but did not correlate with the apoptotic index or microvessel counts. CONCLUSION: Our study shows that cancer cell proliferation rather than apoptosis or angiogenesis is a major determinant of tumor growth rate and survival in patients with locally recurrent rectal cancer.

Adult↗
PubMed2000

Role of synaptophysin in exocytotic release of dopamine from Xenopus oocytes injected with rat brain mRNA.

1. The role of synaptophysin in the exocytotic release of dopamine (DA) was examined in Xenopus laevis oocytes injected with rat brain mRNA. 2. The mRNA-injected oocytes showed DA uptake which depended on the incubation time and external DA concentrations. 3. Stimulation with KCl (10-50 mM) of mRNA-injected oocytes preloaded with DA evoked external Ca2+ -dependent release of DA. The noninjected and water-injected oocytes did not produce uptake of DA and stimulation-evoked release of DA. 4. The high-KCl (50 mM)-stimulated release of DA decreased in the oocytes injected with rat brain mRNA together with antibody to synaptophysin. 5. Immunoblot analysis demonstrated that synaptophysin was expressed in the brain mRNA-injected oocytes but not in the noninjected and water-injected oocytes. 6. Thus, uptake and release machinery similar to native dopaminergic nerve terminals was expressed in Xenopus oocytes by injecting mRNA-extracted from the rat brain, and synaptophysin may play a role in the exocytotic release of DA.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Vascular structure of arteriovenous malformations.

Cerebral arteriovenous malformations (AVMs) are classified angiographically into two types: the arteriovenous fistula (AVF) type and the plexiform type. However, the differences in vascular structure of these two types have not been clarified. The purpose of the present study is to elucidate the vascular structure of plexiform AVMs and to discuss the clinical significance of this classification of AVMs. Specimens of AVMs resected in 8 cases and identified by cerebral angiography as plexiform AVMs were examined. Immediately after their removal, microdissection of the terminal arterial feeder, the nidus, and the venous drainer was performed under a microscope. A histological examination of each element was then conducted. Microdissection of a portion of the vascular mass that formed the nidus made it possible to separate individual vessels of the mass from each other. Many of these individual vessels connected with the feeder on one side, while the other side anastomosed with the drainer, thus exhibiting the morphology of an AVF. From our examination of the AVMs in the present study, we inferred that the plexiform type is fundamentally a conglomeration of AVFs. It is therefore suggested that the vascular structure of this type of AVM is not fundamentally different from that of the AVF type.

Adult↗
PubMed2000

The effect of encephalo-myo-synangiosis on abnormal collateral vessels in childhood moyamoya disease.

Child patients with Moyamoya disease initially present with ischemic symptoms. However, the long-term risk of intracranial hemorrhage for childhood Moyamoya disease is unknown. Hemodynamic overload to the fragile collateral vessels has been considered to cause hemorrhage. We reviewed angiograms to evaluate the effect of encephalo-myo-synangiosis (EMS) on abnormally dilated collateral vessels in 13 child patients with Moyamoya disease. EMS was performed on 24 sides in 13 patients ranging from 5 to 14 years of age. Post-operative angiography (6-88 months after surgery) revealed good revascularizations through EMS (larger than one-third of the middle cerebral artery (MCA) distribution) in 18 sides (75%) and smaller revascularizations in 6 sides (25%). In cases with a good revascularization through EMS, reduction of the abnormal collateral vessels was observed not only in the basal Moyamoya vessels (94% of sides) but also in the medullary arteries derived from the choroidal arteries (62% of sides), which are considered to cause intraventricular hemorrhages in adult patients. It is suggested that EMS may reduce the hemodynamic load on dilated collateral vessels and, subsequently, the long-term risk of intracranial hemorrhage in childhood Moyamoya disease.

Adolescent↗
PubMed2000

Solitary fibrous tumor arising from the falx cerebri--case report.

A 50-year-old female was admitted with headache and visual disturbance. Neuroimaging demonstrated a well-demarcated large tumor attached to the falx cerebri. The tumor was totally removed by surgery. Histological examination showed that the tumor consisted of spindle cells with no pattern in the collagenous background. Staghorn-like blood vessels were common. Immunohistochemical study showed the tumor cells were strongly positive for CD34 and vimentin, but negative for epithelial membrane antigen. The diagnosis was solitary fibrous tumor arising from the falx cerebri. Solitary fibrous tumor is rare within the cranial cavity, and can be distinguished from meningioma and hemangiopericytoma by the histological, ultrastructural, and immunohistochemical findings.

Brain Neoplasms↗
PubMed2000

A rat model for radiation-induced proctitis.

Radiation proctitis is a frequent acute complication encountered with pelvic irradiation. This study was aimed at establishing the optimal radiation dose for radiation-induced proctitis in rats. Female Wistar rats were used. The rectal specimens were examined morphologically at 5th and 10th day following 10-30 Gy irradiation in single fraction. With increasing dose, mucosal damage became worse, and there was a prominent reaction after > or =15 Gy. We selected 17.5 Gy as an optimal dose for radiation proctitis and examined specimens at day 1-14 and at week 4, 6, 8, and 12 after 17.5 Gy. The rectal mucosa revealed characteristic histological changes with time. An edema in lamina propria started as early as 1-2 days after irradiation and progressed into acute inflammation. On day 7 and 8, regeneration was observed with or without ulcer. Four weeks later, all regeneration processes have been completed with end result of either fibrosis or normal appearing mucosa. This study showed that the radiation injury of the rectum in rat develops in dose-dependent manner as it has reported in previous studies and suggested that 17.5 Gy in single fraction is the optimum dose to evaluate the protective effect of various medications for radiation proctitis in face of the clinical situation.

Animals↗
PubMed2000

Endoscopic resection of thyroid tumors by the axillary approach.

One of the problems of surgery in the neck is the scar. Endoscopic surgery has recently been applied to cervical exploration and the scars of the neck are small and inconspicuous, but a few patients still complain of it. For this reason, we developed a technique of endoscopic resection of thyroid tumors using an axillary approach. This approach does not leave a scar on the neck or the chest, and the small scar in the axilla is completely covered by the patient's arm in a natural manner. Furthermore, the complications such as hypercapnia, respiratory acidosis, subcutaneous empysema, air embolism and sensory loss in the neck region are minimized, because the working surgical space is small and procedures can be performed with CO2 insufflation levels below 4 mmHg. We believe that endoscopic surgery by the axillary approach will find a role in the treatment of thyroid tumors

Endoscopy↗
PubMed1999

Magnetite Nanoparticles Prepared by Precipitation from Partially Reduced Ferric Chloride Aqueous Solutions.

Spherical magnetite particles with mean diameter of about 10 nm or less were prepared by means of a reduction-precipitation method with ferric chloride as starting material, which was partially reduced to ferrous salts by Na2SO3 before alkalinizing with ammonia. It was found that the nature of the product depends strongly on the initial ratio R0 = [Fe3+]0/[SO2-3]0. The most appropriate ratio was 3 as proved by X-ray diffraction analysis on the samples although the initial concentration of ferric chloride can be different. Particle diameter increased from ca. 3 to ca. 11 nm with an increase of the concentration of aqueous ferric chloride from 0.075 to 0.45 mol dm-3. The advantage of this method lies in the formation of a red intermediate during the reduction process, which enables us to prevent the reoxidation of the ferrous ions by adding precipitation agents at the end of the reduction reaction without the protection of nitrogen or argon. Copyright 1999 Academic Press.

Journal Article↗