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Biomedical subjects

K Okahara

Publications and source records attributed to K Okahara.

30 records · Page 2Linked to original sources
PubMed1995

[Ventilatory insufficiency due to upper cervical injury treated by diaphragm pacing: a case report].

A 33-year-old man suffered chronic ventilatory insufficiency with tetraplegia after an operation for atlantoaxial dislocation. He was alert and his tetraplegia gradually improved. However, continuous mechanical ventilation was necessary for him. Thirteen months after the operation, a diaphragm pacer (Avery Laboratory Inc.) was implanted on the right phrenic nerve in the cervical region. Nineteen days after the implantation of the right side pacer, a left side diaphragm pacer was also implanted. Diaphragm pacing was started two weeks after the second implantation. The pacing period was gradually prolonged and continuous pacing for 9 hours by the right side pacer and three hours by the left side pacer was able to be obtained. One year after implantation, twelve continuous hours of diaphragm pacing became possible. During diaphragm pacing, blood gas analysis was satisfactory and the patient could move sitting on a wheel chair, watch television and write letters using a word processor. We were unable to achieve total ventilatory support for him using these diaphragm pacers. We thought that the main cause of our partial failure originated from the procedure used in implanting the electrode onto the phrenic nerve. Left side pacing needs higher amplitude than that used on the right side to obtain sufficient tidal volume. The patient refused our continuing the left side pacing because of pain around the anterior chest and shoulder. Another problem to be watched is diaphragm fatigue. However, diaphragm pacing has been continued for six years and it has been useful in improving his quality of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Subendothelial layer of pseudointima of polytetrafluoroethylene graft is formed by transformation of fibroblasts migrated from extravascular space.

A well organised pseudointima is formed in polytetrafluoroethylene (PTFE) grafts within 4 weeks after implantation into inferior vena cava (IVC) of rabbits. To investigate the process of the subendothelial organisation of pseudointima, an animal experiment was conducted. The outer wall of PTFE graft (30 microns fibril length, 3 mm inner diameter, 3 cm long) was coated with 10 um silicon film in the following ways to prevent cellular ingrowth from the extravascular space: non-coating; full-length coating; half-length coating; and full-length coating excluding 5 mm midportion. These grafts were implanted into rabbit IVC and were harvested 4 weeks later. All the grafts were patent but the lumen of the non-coated area was narrowed by pseudointimal hyperplasia. The degree of the hyperplasia estimated by dried tissue deposit was inversely proportional to the length of the coating. The coverage of the luminal surface with endothelial-like cells was noted at anastomotic areas and also at the surface corresponding to the non-coated area. Light microscopy and immunostaining studies on the non-coated midportion revealed the presence of fibroblasts in the interstices of PTFE and smooth muscle cells and myofibroblasts in the pseudointima. Transmission electron microscopy confirmed the presence of myofibroblasts in the midportion of the non-coated area. No transmural capillary ingrowth was observed in the midportion by histological and immunohistochemical analysis. These observations suggest that the subendothelial layer of pseudointima in PTFE grafts is formed by proliferation and transformation of fibroblasts migrating from the extravascular space and that endothelial-like cells may also be derived from such transformation.

Animals↗
PubMed1994

Cutaneous arterial fibromuscular dysplasia: a case report and electron-microscopic study.

A case of a 39-year-old female with fibromuscular dysplasia (FMD) manifesting subcutaneous pulsatile nodules on the right side of her forehead and on her right wrist is reported here. These nodules proved to be FMD aneurysms of the frontal ramus of the right superficial temporal artery and the right radial artery. The patient had also suffered a stroke with subarachnoidal bleeding as a result of this disease. Angiographic examination showed aneurysms in the union and the bilateral vertebral arteries, a branch of the right renal artery, and one the right lumbar artery. A biopsy specimen taken from the frontal branch of the right superficial artery revealed segmental intimal thickening consistent with intimal fibroplasia type FMD upon histological examination. Electron-microscopic findings were also discussed in connection with the histogenesis of the disease. This appears to be the second case of FMD involving arteries in the skin to be reported in the dermatological literature.

Adult↗
PubMed1991

Climbing fiber responses evoked in lobule VII of the posterior cerebellum from a vagal nerve in rabbits.

The vagal afferent projection to the cerebellar posterior lobe was examined in decerebrate rabbits with electrophysiological techniques. Electrical stimulation of a vagal nerve at the cervical region evoked field potential responses on both sides of the posterior vermal cortex from lobule VI to VIII. The most prominent potentials appeared in the ipsilateral medial vermis of lobule VIIa. These potentials had a latency of 15.6 ms, and were negative in the molecular layer and positive in the granular layer. At a stimulation rate of 20 Hz, their amplitude was reduced by 70% of the control value at 1 Hz. Superimposed on these field potentials, unitary complex spikes were recorded at the depths of Purkinje cell layers. These results indicate that the medial vermal cortex of lobule VII receives vagal afferent signals via climbing fibers, which presumably convey cardiovascular information.

Afferent Pathways↗
PubMed1991

Olivocerebellar projection to the cardiovascular zone of rabbit cerebellum.

Climbing fiber responses were evoked in the medial vermal cortex of lobule VIIa by stimulation of the contralateral medial accessory olive (MAO) in anesthetized, paralyzed rabbits. Effective stimulating sites were localized in a small medial part of the caudal MAO, at 0.4-1.6 mm rostral from the caudal pole of the MAO (total length of the MAO, 4.2 mm). Stimulation of this MAO area induced depression in renal sympathetic nerve activity and this depressant response disappeared after ablation of lobule VIIa. Following injections of horseradish peroxidase into the small areas of lobule VIb, VIc, VIIa or VIIb, retrogradely labeled cells were found in corresponding small particular regions of the MAO: lobule VIb to the most caudal part, lobule VIc to the next caudal, lobule VIIa to the most rostral within the caudal MAO, and lobule VIIb further rostrally to the intermediate MAO. There was a clear disparity between the medial halves of lobules VI and VII projected from the medial MAO and the lateral halves from the lateral MAO. These results show that climbing fiber projections to lobules VI and VII are topographically organized, and that the medial region of lobule VIIa, related to cardiovascular function, receives climbing fibers from a localized small medial region of the caudal MAO.

Animals↗
PubMed1991

[Combination of transarterial chemoembolization and endocrine therapy for liver metastases of breast cancer].

Nine patients with multiple metastases including liver from breast cancer were treated with transarterial chemoembolization through hepatic artery using 40-50 mg of 4'-epi-adriamycin and Lipiodol, followed by 800-1,200 mg/day of medroxyprogesterone acetate. Of 9 patients thus treated, there were 4 partial response (44%), 2 no change and 3 progressive disease. Duration of disease control ranged from 4 to 46 months (mean 24.5 months). Seven out of 9 patients died within 6 to 37 months (mean 15.3 months) after diagnosis of liver metastases. The 3- and 5-year survival rates were 45% and 11%, respectively. We conclude that this therapy is a useful treatment modality for controlling liver metastases of breast cancer.

Adult↗
PubMed1990

Unusual intra- and extracranial arteriovenous communication--case report.

The authors report an unusual case of arteriovenous communication between extracranial and intracranial vessels, accompanied by incidentally detected bilateral arachnoid cysts of the middle cranial fossa. A 52-year-old male was admitted with a sudden onset of headache, vomiting, and conjunctival hyperemia of the right eye followed by progressive chemosis and proptosis. He had undergone a craniotomy for hypertensive right putaminal hemorrhage 4 months previously. Angiography showed the main feeding artery to be the superficial temporal artery and the draining veins to be the superficial Sylvian veins and the basal vein of Rosenthal. Partial obstruction of the right cavernous sinus was also shown. At surgery, granulation tissue continued to the dura mater through the skull aperture of previous craniotomy and adhered to the underlying damaged cerebrum. The extremely unusual nature of the communication, the operative findings, and the atypical fistulous figures suggested that communication had occurred postoperatively via newly generated vessels in granulation tissue.

Arachnoid Cysts↗