Ontological foundations for biology knowledge models.

This paper analyzes the ontological requirements for representing biology knowledge, and identifies several areas where current knowledge representation (KR) paradigms need to be extended. We focus on the representation of experimental materials and methods, and the reasoning task of intelligent information retrieval; however, the ontological issues we raise apply to biology (and experimental sciences) in general. We have identified two important concept types in molecular biology that cause problems for standard knowledge models: 1) complex substances such as mixtures and nucleic acid sequences; 2) transformations (such as biochemical reactions) that convert one substances into another. We describe these problems, propose solutions for some of them, and given examples of the need for such knowledge representations in intelligent information retrieval.

Subclavian steal syndrome. A review of 59 consecutive cases.

Subclavian steal syndrome results from reversal of flow through the vertebral artery from occlusion or stenosis of the proximal subclavian or brachiocephalic artery. The resulting "steal" phenomenon leads to the common symptoms of vertigo, syncope, and intermittent claudication of the involved upper extremity. However, these symptoms rarely, if ever, result in permanent neurological damage in and of themselves. A significant percentage of patients will have concomitant extracranial atherosclerotic disease present. Visual disturbances and transient paralysis occur more often in patients with coexistent carotid disease. Carotid artery endarterectomy should be performed first in these patients and will likely resolve all symptoms. Carotid subclavian by-pass using a PTFE graft conduit remains the procedure of choice for patients suffering from disabling symptoms and can be performed with low operative risk and morbidity with excellent long term results.

Creating a knowledge base of biological research papers.

Intelligent text-oriented tools for representing and searching the biological research literature are being developed, which combine object-oriented databases with artificial intelligence techniques to create a richly structured knowledge based of Materials and Methods sections of biological research papers. A knowledge model of experimental processes, biological and chemical substances, and analytical techniques is described, based on the representation techniques of taxonomic semantic nets and knowledge frames. Two approaches to populating the knowledge base with the contents of biological research papers are described: natural language processing and an interactive knowledge definition tool.

Carotid endarterectomy with local anesthesia: results and advantages.

In a collaborative prospective study from two institutions, we reviewed the clinical course of 969 consecutive patients who had 1200 carotid endarterectomies (CEs) for the treatment of occlusive arterial disease during the period 1977 to 1987. The indications for CE comprised transient ischemic attacks (TIAs) in 581 cases (48.4%), cerebral infarction (CI) in 170 (14.2%), monocular blindness in 166 (13.8%), and asymptomatic stenosis in 283 (23.6%). Neurologic monitoring of the awake patient provided more reliable indication of the need for brain protection during operative arterial clamping than did electroencephalography or carotid stump pressure measurement. Of the 1200 cases, 113 (9%) required a shunt as determined by this method. Patients with contralateral carotid occlusion or severe stenosis required shunting six times more frequently than those with a unilateral lesion. Among all procedures, there were nine cases of transient neurologic deficit (0.9%), 11 cases of permanent neurologic deficit (0.9%), and eight deaths (0.67%). Among 283 CEs performed to treat asymptomatic lesions, no strokes and only one death (0.4%) occurred. One hundred sixty-six cases with amaurosis fugax were operated on without stroke or death. In the age group of 70 to 90 years, 508 procedures were carried out with four deaths (0.8%) and three strokes (0.6%). We conclude that CE performed with the patient under local anesthesia is safe and effective and permits satisfactory management of old and high-risk patients.

Extended study of aneurysm formation in umbilical vein grafts.

The rate of aneurysm formation in umbilical vein grafts has been reported to lie between 1% and 8%. However, in these reported series the number of grafts with aneurysms was related to the number of grafts inserted. When the denominator is changed to patent grafts at a given time period, the incidence changes drastically. In this study, duplex scanning was used to detect aneurysms in patent grafts. Four types of aneurysms--localized fusiform, localized eccentric, diffuse, and anastomotic--were recognized. Excluding anastomotic aneurysms, 33% of the grafts patent at 3 years were aneurysmal; in those patent at 4 years, 45% were aneurysmal; and in those patent at 5 or more years, 65% were aneurysmal. On grounds of theoretical considerations, it is believed that duplex scanning is more reliable than either clinical examination or arteriographic study for detecting these aneurysms. There is now evidence that the supporting Dacron mesh is too weak and must be strengthened. Despite aneurysm formation, the patency rate in our series has remained second only to saphenous vein grafts, as previously reported.

Minimizing the risks of carotid endarterectomy.

In 1971 this study was undertaken to determine optimal methods and guidelines for lowering the mortality and neurologic complication rates associated with carotid endarterectomy. Of 570 carotid endarterectomies, 481 (84%) were performed under local anesthesia to provide continuous neurologic monitoring and to permit operation on the very elderly and poor-risk patient. In 418 of these procedures carotid stump pressures (CSPs) were measured with patients awake to determine the level of back pressure sufficient for brain protection during operative occlusion. Selective shunting was necessary in 40 (8%) of these cases. Of 78 patients with a CSP of 0 to 25 mm Hg, only 39 (50%) required shunting. Only one patient with a pressure greater than 25 mm Hg (29 mm Hg) needed a shunt. The CSP/brachial blood pressure (BBP) index was calculated for 410 procedures. Of 97 patients with a CSP of 0 to 30 mm Hg, only 31 required a shunt (CSP/BBP index 0.01 to 0.18). No shunt was necessary for an index greater than 0.18. Patients with a contralateral occlusion or severe stenosis required a shunt six times more frequently than those with unilateral disease. For 570 procedures the overall mortality rate was 0.7% and the neurologic complication rate was 0.9%. When local anesthesia was used for 481 procedures, there was only one death (0.2%). For 74 asymptomatic lesions there were no deaths or stroke. Neurologic monitoring under local anesthesia and CSPs are reliable indicators for selective shunting. Multiple-risk factors influence the outcome of carotid endarterectomy, but most can be avoided.

Surgical therapy for recent total occlusion of the internal carotid artery.

From January 1980 until May 1983, 24 patients had surgical exploration of the carotid bifurcation for suspected recent total occlusion of the internal carotid artery (ICA). All patients had recent onset of neurologic symptoms related to the ipsilateral cerebral hemisphere. Selective carotid angiography determined preoperative total occlusion of the ICA. Because surgery failed to reopen the ICA in nine patients, they had endarterectomy of the external carotid artery. Fifteen patients had initially successful thromboendarterectomy of the ICA. Prior to patient dismissal, patency was documented by B-mode ultrasound or digital subtraction angiography (DSA). All 15 patients had another B-mode ultrasound scan or DSA at least 45 days after thromboendarterectomy. On reexamination four ICAs were reoccluded, but only one patient became symptomatic. There were no operative deaths and no increase in preoperative neurologic deficits. The natural history of patients with total occlusion of the ICA is variable. The most important factor influencing a therapeutic decision is the patient's neurologic status. This study supports an aggressive, early surgical intervention for recent total occlusion in carefully selected patients.

Revascularization of the femoropopliteal arteries using saphenous vein, polytetrafluoroethylene, and umbilical vein grafts. Five- and six-year results.

Saphenous vein (SV), polytetrafluoroethylene (PTFE), and umbilical vein (UV) grafts placed in the femoropopliteal or tibial areas for occlusive arterial disease were compared for the years between 1975 and 1982. In proximal v distal popliteal replacement, the early failure rate differed only in PTFE grafts to relieve ischemia, with below-knee failure being worse. In all femoropopliteal grafts for claudication, the SV were better than the UV grafts. When done for ischemia, the SV were better than the UV grafts. When done for ischemia, the SV were better than the PTFE grafts. By life-table analysis, SV grafts done for claudication or for ischemia were superior to PTFE grafts. The UV grafts also were better than PTFE grafts. Arteriography showed marked aneurysmal dilatation in a UV graft in the common femoral to popliteal to anterior tibial area at 50 months. In a second patient, mild aneurysmal dilatation was seen. The UV graft is acceptable when SV is not available. The PTFE graft across the knee gives poor results but above the knee is comparable with UV grafts.

Obliterative arterial disease of the upper extremity.

During the past 20 years, 163 patients had 194 operations for obliterative arterial disease of the upper extremity. Of these, 68 had neurological symptoms primarily that were associated with arterial obstruction of the first portion of the subclavian artery. The remaining 95 patients had ischemic symptoms of the upper extremity, namely, intermittent claudication of the arm or ischemic necrosis of the fingers. There were 95 procedures performed on 90 patients with diminished or absent brachial blood pressures. There were 89 cervical sympathectomies performed on patients whose brachial pressures were equal to the contralateral arm. When sympathectomy was done, results were excellent in patients who had a rise in skin temperature confirmed preoperatively by reflex vasodilation studies. An aggressive approach with early diagnostic arteriography and appropriate surgical therapy is indicated in patients with ischemia to the upper extremity.

Surgical management of the totally occluded internal carotid artery: a ten-year study.

Although surgical treatment of the stenotic and ulcerative internal carotid artery has been accepted as an effective approach to the management of cerebrovascular insufficiency, uncertainty and controversy have prevailed over the past two decades regarding the optimal management of the totally occluded artery. Over a 10-year period, 47 thromboendarterectomies were performed for recent total occlusion of the internal carotid artery. The patients were categorized and selected for surgery according to their neurologic manifestations and clinical status. Postoperative patency was studied by angiography and noninvasive laboratory tests, including oculoplethysmography, carotid phonoangiography, Doppler ultrasound, and ultrasonography. The patency rate achieved appeared to be related to the duration of carotid occlusion (100% within 7 days and 50% at 1 month). The overall patency rate was 68%. There were no operative deaths or morbidity. Dramatic improvement occurred in three patients who underwent surgery immediately after the onset of a major neurologic deficit. The results of this study indicate that surgical treatment for internal carotid occlusion should be considered in selected circumstances. Careful case selection and judicious timing of operation are mandatory.

Newer prosthetic material compared with autogenous saphenous vein for occlusive arterial disease of the lower extremity.

This article reports our experience with 101 polytetrafluoreoethylene and 102 umbilical vein grafts inserted into the femoropopliteal and femorocrural arteries of 98 and 97 patients, respectively, during the last 5 years. These grafted extremities are compared to 416 saphenous vein grafts placed in similar arteries of 383 patients during the past 18 years. The operations were performed by seven surgeons associated in private practice. During this period of time, all records were collated by our research associate, R. M. Preuninger, Ph.D., and the life-table analyses of the data were computed by S. Mehta of the Gore-Tex Company, using the method of Peto et al.

Subclavian steal syndrome. A 12-year experience.

Over a 12-year period, 43 operations were performed on 40 patients for correction of the subclavian steal syndrome. Eleven of these patients also underwent endarterectomy for coexisting carotid artery disease. There were 16 transthoracic procedures and 27 transcervical procedures. Graft failure in two patients was corrected by a second operation. There was one early death and one late death. The remaining 38 patients have been carefully studied for up to 12 years, with an average follow-up period of 60 months. These 38 patients have remained asymptomatic and their revascularization procedures have remained functional, as determined by blood pressure determinations in the involved extremity and, in some cases, by arteriography.