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Biomedical subjects

J R Stewart

Publications and source records attributed to J R Stewart.

At least 109 records · Page 6Linked to original sources
PubMed1987

Postoperative radiation therapy for pathologic stage C prostate cancer.

From 1971 to 1981, 26 patients with pathologic Stage C prostate cancer were referred to this department for postoperative radiation therapy. During the same period 24 patients, undergoing radical prostatectomy at this institution, were found to have pathologic Stage C disease but did not receive adjuvant irradiation. Both groups of patients are compared at 5 years post surgery for disease-free survival, local control, and distant failure in an attempt to determine whether there is a demonstrable benefit of adjuvant irradiation in this setting. All irradiated patients started therapy 1 to 4 months post surgery. All were treated with megavoltage irradiation. The majority were treated to the pelvis by a 4-field technique to an absorbed dose of 46-50 Gy followed by a prostate boost via multiple fields to a total dose of 54-70 Gy. Three patients received 50-52 Gy to the pelvis only and 5 patients received 56-65 Gy to localized prostate fields only. Moderate complications in the irradiated group were 23% with no severe complications observed. This rate may be reduced with treatment of local prostate fields only. There was no significant difference in 5-year survival, 5-year disease-free survival, or distant metastases in patients treated with surgery only or surgery plus radiation. However, local recurrence at 5 years was significantly different (p = 0.046), 16.6% in the surgery only group and 0 in the irradiated group. This difference was more pronounced in the subset of patients with seminal vesicle invasion: 30% local recurrence in the surgery only group versus 0 in the irradiated group. These data suggest that the addition of postoperative irradiation in pathologic Stage C prostate cancer yields an improvement in local control, and that for the subset of patients at significant risk of local relapse, those with seminal vesicle invasion, adjuvant prostate bed irradiation should be recommended.

Combined Modality Therapy↗
PubMed1987

Effects of dietary fiber, carbohydrate, lipid and protein levels on serum and liver lipids in rats.

Response-surface regression analysis was used to study dietary levels of fiber, carbohydrate, lipid and protein to minimize serum and liver cholesterol and triglyceride levels and maximize serum high-density lipoprotein-cholesterol levels of male weanling rats. Because the dietary components were not statistically independent, they were studied in combinations of three variables. The three-variable combinations were the most useful in locating the desired maximum or minimum lipid responses in terms of the proportions of the dietary components. These analyses indicated that dietary carbohydrate, lipid and protein were better than dietary fiber for predicting the serum and liver lipid response levels. Response-surface contours and three-dimensional plots were developed for each lipid response except serum triglycerides, which were not predictable. The contours and three-dimensional plots were used to help determine those combinations of the diet components that would produce the desired maximum or minimum lipid responses. The statistical analyses indicated that the desired lipid response levels could be attained with a diet consisting of 3-5% neutral detergent bran fiber, 6-10% lipid, 54-55% carbohydrate, 26-30% protein and 4.7% vitamins and minerals.

Animals↗
PubMed1987

Free radical-producing enzyme, xanthine oxidase, is undetectable in human hearts.

Samples from four human hearts were analyzed for both their xanthine dehydrogenase and xanthine oxidase content. We used the conventional spectrophotometric assay and a more sensitive fluorometric assay to determine the content of enzyme in these samples. In no case could any activity be detected. We conclude that human hearts must contain less than 2.0 nU/g of activity. This makes it unlikely that xanthine oxidase is a significant source of O2 free radicals in the ischemic human heart or that xanthine oxidase inhibitors will be of therapeutic value in that setting.

Animals↗
PubMed1987

Renal tubular secretion of the alkanesulfonate 2,3-dimercapto-1-propanesulfonate.

The in vivo tubular secretion and metabolism of 2,3-dimercapto-1-propanesulfonate (DMPS) was examined in the chicken by use of the Sperber technique. Infusion of DMPS into the renal portal circulation of the chicken at rates equal to or less than 7.5 mumol X min-1 X kg body wt-1, resulted in a tubular excretion ratio of 0.5 for DMPS with 90% of the infused DMPS excreted in the urine unchanged. Renal tubular secretion accounted for approximately 90% of the total DMPS excreted into the urine during the infusion of DMPS at a rate of 0.75 mumol X min-1 X kg-1. The secretion of DMPS was saturable and was inhibited by p-aminohippurate (PAH), probenecid, and heptanesulfonate. Taurine (2-aminoethanesulfonate), isethionate (2-hydroxyethanesulfonate), and 2-mercaptoethanesulfonate had no effect on the secretion of DMPS or PAH. Renal tubular secretion may explain several pharmacological characteristics previously reported for DMPS, including the selective removal of heavy metals from the kidney.

Alkanesulfonates↗
PubMed1986

The potentiating effects of alcohol on driver injury.

It is well established that alcohol (ethanol) is associated with increased probability of traumatic injury. This relationship has been attributed to alcohol's impairment of judgment and psychomotor performance, leading to increased probability of an injury-producing mishap. Once an accident occurs, it is widely believed that alcohol may protect against injury. However, controlled laboratory studies using animal models indicate that alcohol exacerbates the injurious effects of trauma. In this study, detailed analysis of data from more than 1 million drivers involved in motor vehicle crashes indicates that when the effects of injury-related variables such as safety belt use, vehicle deformation, vehicle speed, driver age, and vehicle weight are taken into account, the drinking driver is more likely to suffer serious injury or death compared with the nondrinking driver. These findings do not support the widespread belief that alcohol is protective against injury, but rather indicate that alcohol increases vulnerability to injury in any given crash.

Accidents, Traffic↗
PubMed1986

Effects of coumadin on the resolution of canine venous thrombi.

Experimental thrombosis of the inferior vena cava was induced in 39 dogs to create a thrombus that could be embolized to a Greenfield filter for measurement of thrombolytic activity. In the series of 17 control animals, thrombus weight had decreased from 0.871 +/- 0.10 g to 0.477 +/- 0.08 g (P less than 0.05) at 2 weeks and from 0.884 +/- 0.097 g to 0.106 +/- 0.025 g (P less than 0.001) at 4 weeks representing 56 and 12%, respectively, of initial weight. In the series of 22 animals treated with coumadin, the resolution in thrombus weight was from 0.849 +/- 0.13 g to 0.171 +/- 0.14 g (P less than 0.02) at 2 weeks and from 1.031 +/- 0.34 g to 0.013 +/- 0.013 g (P less than 0.05) at 4 weeks representing 20 and 1%, respectively, of initial weight. These results show that in this model where venous flow is preserved around a trapped thrombus, lysis proceeds at a significant rate, yet can be accelerated by therapeutic levels of coumadin.

Animals↗
PubMed1986

Free radical scavengers and myocardial preservation during transplantation.

The efficacy of oxygen radical scavengers in preservation of left ventricular (LV) function after prolonged hypothermic global ischemia was investigated in a model of orthotopic cardiac transplantation in sheep. Group 1 hearts (N = 8) received hypothermic crystalloid cardioplegic solution, and were harvested and stored at 4 degrees C in balanced electrolyte solution for six hours prior to transplantation. Group 2 (N = 9) received identical treatment with the addition of 30,000 units of superoxide dismutase to the cardioplegic solution and the administration of 60,000 units of superoxide dismutase coincident with reperfusion. All animals were weaned from cardiopulmonary bypass. Preischemic and postischemic LV function was determined using sonomicrometry and a micromanometer-tipped LV catheter. Coronary blood flow was determined using standard microsphere techniques, and platelet deposition was assayed with autologous platelets labeled with indium 111. Lipid peroxidation products were measured using thiobarbituric acid assay. LV performance was significantly better (p less than .05) in Group 2 hearts when assessed by the slope of the end-systolic pressure-volume relationship and the stroke work versus end-diastolic volume relationship. There was better preservation of endocardial blood flow in the group receiving superoxide dismutase compared with controls (p less than .05). Platelet deposition, as determined by the tissue to blood ratio of scintigraphic counts, was greater (p less than .05) in controls compared with the group receiving superoxide dismutase. In addition, thiobarbituric acid reactive species were significantly less (p less than .05) in Group 2 versus Group 1 hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Surgical management of patients with pulmonary valve dysplasia.

Pulmonary valve dysplasia is a distinct pathological entity consisting of markedly thickened, deformed, and largely immobile pulmonary valve leaflets. The clinical features and surgical management of 21 consecutive patients operated upon between 1975 and 1985 were reviewed. Mean age at operation was 26.7 months (range: 1 month to 9.5 years). Initial surgical intervention in 3 patients consisted of closed valvotomy or systemic pulmonary artery shunt. One of these patients subsequently had a partial pulmonary valvectomy; the other 2 had total valvectomy and pulmonary annuloplasty. Two patients had partial valvectomy as a primary procedure, and 1 has subsequently required total valvectomy and annuloplasty. Sixteen patients initially had total pulmonary valvectomy, 4 with a simultaneous transannular outflow tract patch. One patient subsequently required a transannular outflow tract patch. Therefore, definitive repair consisted of partial valvectomy in 2 patients, total valvectomy in 19, and a transannular outflow tract patch in 9 patients with a hypoplastic pulmonary annulus. There were no operative deaths, and all patients are asymptomatic at a mean follow-up of 37.9 months. Five patients who underwent total valvectomy were catheterized postoperatively. The mean residual gradient was 25 mm Hg. Pulmonary valvectomy appears to provide both effective relief of stenosis and long-term asymptomatic status in patients with pulmonary valve dysplasia. Total excision of all valve leaflets is recommended. Careful consideration should be given to a simultaneous transannular outflow tract patch if the annulus is hypoplastic.

Child↗
PubMed1986

Regional hyperthermia for clinically advanced deep-seated pelvic malignancy.

Forty-three patients with deep-seated pelvic malignancy have been treated at the University of Utah on a pilot protocol involving regional hyperthermia (HT) produced by the BSD-1000 HT system and the annular phased array applicator (AA) usually driven at 60 MHz. Acute toxicity consisted primarily of pain within the AA aperture (74%), pain outside the aperture (33%), and bladder spasm (26%) or systemic stress (25%). Systemic stress only infrequently was power limiting. The most common power-limiting factors were pain (33%) and excessive heating of normal tissues (23%). In 9 patients (21%), there was no power-limiting factor. Treatment-related complications were uncommon and consisted of superficial second degree burns (3 patients), small bowel obstruction (1 patient), and rectal fistula (1 patient), all of which resolved with supportive nonsurgical therapy. Detailed thermal mapping and thermal dosimetry were performed on 36 patients. Thermal dosimetry parameters were all rather disappointing; however, the protocol prioritized the prevention of complications, and patients with acute toxicity or other power-limiting factors were not pushed to achieve high thermal doses. A logistic regression analysis was performed to determine if any factors were correlated with response (PR + CR). "Concurrent radiation dose" and "number of satisfactory heat treatments" were highly and independently correlated with response (p = 0.002). Responders (median survival = 10 months) survived significantly longer (p = 0.0014) than nonresponders (median survival = 4 months). Four of the responders are alive and currently without evidence of disease.

Humans↗
PubMed1986

Abdominal regional hyperthermia with an annular phased array.

Twenty-eight patients with advanced upper-abdominal malignancy were treated at the University of Utah on a pilot protocol involving regional hyperthermia (HT) produced by the BSD-1000 HT system and the annular phased array applicator (AA), usually driven at 60 MHz. Eighty-two percent of the patients had widespread metastatic disease, and the mean tumor burden was 2,900 cc. Seventy-nine percent of the patients received concurrent radiotherapy. Acute toxicity consisted primarily of pain within the AA aperture (43%), systemic stress (43%), and nausea or vomiting (29%). Systemic stress was the most frequent power-limiting factor (46%). There were two treatment-related complications: sciatic neuritis from intramuscular injection (one) and pleural effusion from thermometry probe placement (one). Detailed thermal mapping and thermal dosimetry were performed on 26 patients. The mean thermal dosimetry parameters were quite low. Concurrent radiation doses were also quite low (mean, 1,500 rad) to avoid toxicity of sensitive organ systems within the abdomen. The objective response rate was only 18%, all partial, but 43% of the patients achieved effective symptomatic palliation. The five objective responders did survive significantly (P = .02) longer than the 23 nonresponders.

Abdominal Neoplasms↗
PubMed1986

Cell kill and tumor control after heat treatment with and without vascular occlusion in RIF-1 tumors.

RIF-1 tumors (100-300 mg) were exposed in vivo to heat treatment (41-48 degrees C) for 30 min and then assayed for either cell survival or tumor control. The tumors were heated either with normal perfusion or with temporary vascular occlusion (clamped for 30 min prior to and during the 30-min treatment). The physical technique of water bath heating ensured temperature uniformity in both the perfused and vascularly occluded tumors. Survival curves for tumor cells heated under both conditions had a shoulder and exponential regions. While the T0's were not statistically different in the two cases, cells from the tumors whose blood flow had been occluded showed an enhanced sensitivity to heat as evidenced by a reduction of the shoulder by 2.5 degrees C. A similar increase in sensitivity was measured with the tumor cure assay with the TCT50 decreasing from 47 degrees C for unclamped tumors to 45 degrees C for clamped tumors. The two assays are therefore in excellent agreement in assessing the effectiveness of heat treatment and the influence of vascular occlusion on the heat sensitivity of this tumor. Since the clonogenic assay was performed immediately after treatment, this agreement between assays indicates that direct cell kill by heat is the major factor in determining cure in this tumor.

Animals↗
PubMed1986

Hemorrhage vs rethrombosis after thrombolysis for acute myocardial infarction.

To determine whether or not the timing of heparin infusion affects either bleeding or reocclusion following intracoronary streptokinase for acute myocardial infarction, heparin was infused immediately after streptokinase in 89 patients and was delayed for 12 hours in the subsequent 93. Bleeding occurred in 22 immediate-heparin patients and was major in five (one fatal); there were 14 hemorrhages in the delayed-heparin group, all minor. At discharge, reocclusions were observed in 18% (12/68) of immediate-heparin patients, and 11% (3/27) of the latter. Bioassayed fibrinogen levels displayed sustained depression regardless of bleeding for 20 hours after streptokinase; however, defibrinogenation measured by immunoassay was much less striking. This suggests that high levels of fibrinogen degradation products spuriously affect the bioassay of fibrinogen. We conclude that bleeding is related to the anticoagulant effects of fibrinogen degradation products interacting with heparin, and may be largely independent of hypofibrinogenemia. Delaying heparin for 12 hours may decrease the risk of bleeding while little affecting the risk of reocclusion.

Coronary Disease↗
PubMed1985

Electron arc therapy: physical measurement and treatment planning techniques.

An electron beam arc therapy technique has been developed for the treatment of the post-mastectomy chest wall using a clinical linear accelerator modified for arc therapy. The effects on the dose distribution of primary X ray collimators, secondary cerrobend blocks attached to the accelerator accessory tray, and tertiary cerrobend casting of the treatment area on the patient's thorax have been investigated. Multiple electron energies within the same arc, variable rad per degree, and variable shaped secondary and tertiary applicators have been employed to optimize dose uniformity across the treated surface. A computerized treatment planning program has been developed to aid in visualization and optimization of dose distributions. A simple technique to estimate the width variation in the secondary collimator necessary to compensate for radial patient thickness changes in the cephalocaudad direction is described. Electron beam energies of 6 MeV, 9 MeV, 12 MeV, 15 MeV, and 18 MeV have been studied. The physical measurements needed to implement this technique are described, and a comparison of electron arc therapy dose distributions with other standard treatment techniques is presented.

Breast Neoplasms↗
PubMed1985

A comparison of deep regional hyperthermia from an annular array and a concentric coil in the same patients.

Twenty-two patients with advanced pelvic or abdominal malignancy (or both) were treated on successive occasions with hyperthermia produced by an annular array (AA) (60-80 MHz, 500-1800 W forward power) and a concentric coil (CC) (13.56 MHz, 350-1000 W forward power). Both devices were compared with respect to acute toxicity and power limitations. There was no power limiting factor in pelvic heating in 7/14 patients treated with the AA, however 13/14 experienced power limiting sacrococcygeal pain with the CC. The 9 patients who underwent abdominal heating had a variety of power limitations with both devices. Thermal mapping was performed in 23 treatments with the AA and in 19 with the CC. Composite thermal maps of patients with similar thermometry sites show that heating patterns produced by the CC were predictable from theory and static phantom measurements. The AA achieved broader regional heating, particularly at depth, but heating patterns were less predictable. Spatial thermal dose (TD) analysis revealed higher minimum tumor TDs and more favorable mean tumor/normal tissue TD ratios with the AA than with the CC. We conclude that the AA is superior to the CC for pelvic treatment and that both devices have limitations in abdominal treatment.

Abdominal Neoplasms↗