Biomedical subjects
Publications and source records attributed to R W Harris.
Clostridium perfringens theta-toxin was shown to lyse target erythrocytes by a colloid-osmotic mechanism. Analysis showed the onset of lysis of erythrocytes by theta-toxin could be temporarily stabilized with 0.3 M sucrose. Flow cytometry analysis of the size distribution of theta-toxin-treated erythrocytes showed swelling of the erythrocytes prior to lysis.
Although balloon angioplasty for the management of failing bypass grafts has been well documented, little mention has been made of its use in treating the occlusive lesion within the native artery after a failed bypass graft. We report our experience with five patients in whom successful balloon angioplasty was carried out subsequent to failure of a femoral popliteal bypass graft. Increasingly aggressive percutaneous therapy of arterial occlusive disease may now be expanded to include a unique group of patients with chronically failed bypass grafts and occlusive disease within the native artery conducive to percutaneous transluminal angioplasty. This group of patients would previously have been relegated to repeat bypass grafts with its inherently inferior patency and recognized added technical demands. Percutaneous balloon angioplasty appears to be a plausible alternative in selected cases for repeat lower extremity revascularization.
Speech recognition was assessed under three levels of room reverberation, each in quiet and noise, for subjects with varying amounts of sensorineural hearing impairment. The three acoustic environments were: sound suite, reverberant room with a reverberation time (T) = 0.54 s and reverberant room with T = 1.55 s. Three groups of subjects were utilized: normal hearing, mild sensorineural hearing impairment and moderate-to-severe sensorineural hearing impairment. Speech recognition ability for each of the three groups of subjects significantly differed from the other two groups for each of the three reverberant conditions. The detrimental influences of noise and reverberation increased with the magnitude of hearing impairment. In addition, there was an interaction between noise and room reverberation, where the detrimental effects of room reverberation were compounded by the addition of noise.
We placed 20 bypass grafts to the lateral plantar artery in 18 extremities to salvage feet with wet (12) or dry (six) gangrene; 15 grafts were implanted in men (75%), and five were implanted in women (25%). The median age was 65 years. All except two patients had diabetes; eight were treated with insulin. One patient had Buerger's disease, and another had vasculitis with chronic lymphocytic leukemia. History of smoking (65%), hypertension (53%), heart disease (71%), and osteomyelitis in the foot (35%), were noted. Cultures were positive in 15 gangrenous feet, 11 with gram-negative bacilli. Four long femoroplantar bypasses were placed. Ten short grafts were placed from the popliteal artery, and six jump grafts were placed distal to a femoropopliteal or tibial bypass. Hospital stay ranged from 8 to 38 days (median 16 days), and there were two in-hospital deaths. Transmetatarsal or button toe amputations were performed in nine feet. There were two below-knee amputations, one with a patent graft, for a foot salvage rate of 89% at 2 months. In four instances the gangrenous ulcers took longer than 6 months to heal; all other wounds healed within 6 months. The primary and secondary patency rates were 85% at 1 month, and 73% at 3 months and thereafter. Four of five graft failures occurred in the two legs with repeat bypass graftings. All patients with successful revascularization are able to walk, and seven returned to work full time.
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We measured ankle/arm pressure indexes and blood flow rates before and after performing percutaneous transluminal angioplasty in 36 extremities. Flow rates through the leg were determined with a magnetic resonance blood flow scanner. All patients had claudication; one had gangrene, another had an ulcer, and two complained of rest pain. The median age was 65 years, and 72% were men. There were 25 dilations of the iliac artery, 12 of the superficial femoral artery, and eight of the popliteal arteries; nine patients had two arterial segments dilated. Nineteen legs had ankle/arm pressure indexes before percutaneous transluminal angioplasty of less than 0.80 (range 0.51 to 0.75); their flow rates averaged 40 +/- 20 (SD) ml/min. After percutaneous transluminal angioplasty flow and pressure increased significantly in 14 of these 19 legs, and three had no hemodynamic improvement; in one leg only pressure and in another only flow increased significantly. The remaining 17 extremities had ankle/arm pressure indexes before percutaneous transluminal angioplasty ranging from 0.81 to 1.09; their flow rates averaged 53 +/- 27 (SD) ml/min. Abnormal flow rates were detected in 15 of these 17 extremities. With near-normal ankle/arm pressure indexes no significant increase in pressure was anticipated. Flow rates augmented to 75 +/- 28 (SD) ml/min after percutaneous transluminal angioplasty; a significant increase in flow was noted in 12 legs (71%). For patients with ankle/arm indexes before percutaneous transluminal angioplasty of less than 0.80, either pressure or flow measurements should corroborate the benefits of the operation, whereas if the ankle arm index is greater than 0.80, flow measurements are most likely to substantiate changes in peripheral hemodynamics.
A two microphone adaptive digital noise cancellation technique was used to improve word-recognition ability of normally hearing and hearing-impaired subjects in the presence of varying amounts of multitalker speech babble noise and speech spectrum noise. Signal-to-noise ratios varied from -8 dB to +12 dB in 4 dB increments. The adaptive noise cancellation technique resulted in reducing both the speech babble and speech spectrum noises 18 to 22 dB. This reduction in noise resulted in average improvements in word recognition, at the poorest signal-to-noise ratios, ranging from 37% to 50% for the normally hearing subjects and 27% to 40% for the hearing-impaired subjects. Improvements in word recognition in the presence of speech babble noise as a result of adaptive filtering were just as large or larger than improvements found in the presence of speech spectrum noise. The amount of improvement of word-recognition scores was most pronounced at the least favorable signal-to-noise ratios.
Two hundred forty-three bypasses to paramalleolar arteries were performed in 224 extremities of 208 patients since 1971; 166 were implanted in men (68%) and 77 in women (32%). The median age was 73 years. Gangrene (61%), nonhealing ulcer (15%), rest pain (22%), and trauma (2%) were the indications for bypass. Usual risk factors were noted: diabetes (65%), smoking (51%), heart disease (46%), and hypertension (45%). The extent of occlusive disease dictated three graft configurations: long grafts originating in arteries proximal to the adductor tendon (n = 111), short grafts originating at or below the popliteal artery (n = 88), and jump grafts originating near the distal end of a previous femorodistal bypass (n = 44). The association between diabetes (incidence 80%) and gangrene (75%) in patients with short grafts was statistically significant (p less than 0.01). The 2-year secondary patency rate of long in situ grafts was 92% compared with 72% for other autogenous vein long grafts. The limb salvage rate for all autogenous vein long grafts was 90% at 3 years. The secondary patency rate at 3 years for short grafts was 81% and the limb salvage rate was 80%. There were four amputations with patent grafts. Primary and secondary patency rates of jump grafts were similar (53%), whereas the limb salvage rate was 89% at 2 years. Patency and limb salvage rates of rarely employed nonautogenous conduits were less than 35% at 1 year (long grafts). Bypass grafts to the ankle and foot are effective and durable and should be performed with autogenous vein.
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Neointimal hyperplasia at the proximal anastomosis of a femorodistal bypass can be managed by dividing the autogenous vein graft and transposing the proximal anastomosis from the common femoral to the deep femoral artery. The method obviates repeat dissection of the graft and femoral arteries in the groin.
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The possible benefit of either partial splenectomy or splenic autotransplantation as protection against post-splenectomy sepsis was investigated. Sprague-Dawley rats were challenged with intravenous Streptococcus pneumoniae and the incidence of bacteremia and mortality were recorded. Animals were divided into four groups based upon the amount of splenic tissue conserved: total splenectomy (0%), partial splenectomy (62%), splenic autotransplantation (27%), or sham celiotomy (100%). A statistically significant (P 0.05) decrease in the incidence of septic death was seen in comparing the total splenectomized animals (63%) to the autotransplant group (27%), the partial splenectomy (4%) and the control group (4%). This diminishing mortality is inversely proportional to the amount of splenic remnant in the respective groups. There was a similar, parallel relationship in the incidence of Streptococcus pneumoniae bacteremia. Thus, the greater the amount of remaining splenic tissue, the lower the incidence of bacteremia and subsequent mortality, implying the preservation of immunologic function with splenic conservation.
A major complaint of individuals with normal hearing and hearing impairments is a reduced ability to understand speech in a noisy environment. This paper describes the concept of adaptive noise cancelling for removing noise from corrupted speech signals. Application of adaptive digital signal processing has long been known and is described from a historical as well as technical perspective. The Widrow-Hoff LMS (least mean square) algorithm developed in 1959 forms the introduction to modern adaptive signal processing. This method uses a "primary" input which consists of the desired speech signal corrupted with noise and a second "reference" signal which is used to estimate the primary noise signal. By subtracting the adaptively filtered estimate of the noise, the desired speech signal is obtained. Recent developments in the field as they relate to noise cancellation are described. These developments include more computationally efficient algorithms as well as algorithms that exhibit improved learning performance. A second method for removing noise from speech, for use when no independent reference for the noise exists, is referred to as single channel noise suppression. Both adaptive and spectral subtraction techniques have been applied to this problem--often with the result of decreased speech intelligibility. Current techniques applied to this problem are described, including signal processing techniques that offer promise in the noise suppression application.
Nonthrombotic iliofemoral venous obstruction, masquerading as deep vein thrombosis, was diagnosed in four patients. In each instance the patient was hospitalized and intravenous heparin therapy was started. Phlebography demonstrated venous outflow obstruction without thrombosis; subsequent CT scanning revealed an obstructing lesion in each case. At surgical exploration, (1) endoaneurysmorrhaphy of a hypogastric artery aneurysm decompressed an obstructed right iliac vein; (2) a primary iliac vein leiomyosarcoma was extirpated; (3) a synovial cyst arising from the right hip joint, which obstructed the femoral vein, was excised; and, (4) a postherniorrhaphy inflammatory mass obstructing the left iliofemoral vein junction was confirmed with biopsy results. Improved diagnostic accuracy with its attendant specific therapy is achieved in suspected cases of iliofemoral vein thrombosis if, in addition to noninvasive venous studies or phlebography, CT scanning of the abdomen and pelvis is performed.
When a suitable single length of saphenous or arm vein is unavailable, the elderly patient with a profoundly ischemic extremity, poor runoff, and a distal outflow vessel frequently undergoes amputation. Rather than performing primary amputation or resorting to nonautogenous conduites, we used 21 different combinations of available vein segments of ipsilateral or contralateral greater saphenous, lesser saphenous, cephalic, and basilic veins as composite autogenous bypass grafts. Fifty-four extremities, of which 21 (39%) had one or more failed previous bypasses, were revascularized. Tissue necrosis necessitated operation in 74% (40 instances) and rest pain in 19% (ten instances). All grafts extended below the knee, 22% (12 grafts) to the infrageniculate popliteal artery, 78% (42 grafts) to an infrapopliteal runoff vessel, and 28% (15 grafts) to the ankle or foot. The patency rate at one month was 81%. Thrombectomy alone or with local graft repair increased the one-month patency rate to 96%. At one year, the patency and limb salvage rates were 74% and 82%, respectively.
The concentrations of retinol and beta carotene were measured in serum samples taken from 113 women with cervical cancer, 32 with invasive and 81 with pre-invasive disease, and compared with those from 226 age-matched control women. There was little difference in serum retinol levels between women with cancer of the cervix, at any stage, and the control women, after adjusting for potential confounding factors. Serum beta carotene concentrations were likewise similar in women with invasive disease and the controls. However mean beta carotene levels were significantly reduced in women with pre-invasive disease compared to the controls (221.3 cf. 291.6 micrograms l-1, P less than 0.05). This reduction was more evident amongst women with a diagnosis of carcinoma-in-situ (mean 213.1 micrograms l-1 than amongst those with severe dysplasia (mean 228.7 micrograms l-1. There is a negative trend between beta carotene and risk of pre-invasive disease which is of borderline significance. These data have also been used to investigate the effects of smoking and oral contraceptive usage on the serum levels of retinol and beta carotene. Both habits tend to increase retinol and decrease beta carotene concentrations.
A case of acute aortic occlusion caused by embolization of malignant melanoma tumor fragments is presented. Transfemoral catheter embolectomy restored normal lower extremity circulation. Noncardiac tumor emboli, although rare, originate either from primary pulmonary malignancies or nonpulmonary malignancies with pulmonary metastases and pulmonary vein invasion. Tumor embolization should be considered a possible source of peripheral arterial emboli when there is no other obvious source, such as the fibrillating or infarcted heart. In such cases, early surgical intervention should be considered in preference to therapy with heparin or streptokinase.
Preoperative noninvasive imaging of the veins of the upper extremities has been included in the protocol to select an autogenous vein for a distal bypass in the lower extremity. Arm veins are sought as bypass grafts when the saphenous vein is absent or not usable. Duplex ultrasound provided images of the cephalic and basilic veins in 10 patients in whom visual inspection failed to reveal usable grafts. All arm veins implanted were at least 2 mm (range 2 to 6 mm) in internal diameter determined by ultrasound and were, on the average, 2 mm larger when unroofed. This noninvasive technique has decreased the number of fruitless surgical explorations to obtain a suitable arm vein and has increased the use of arm veins by revealing veins previously not anticipated by physical examination, which virtually eliminated the use of nonautogenous conduits in our practice.