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Biomedical subjects

L Shelton

Publications and source records attributed to L Shelton.

18 recordsLinked to original sources
PubMed1995

Acid hydrolysis of monoclonal antibodies.

For analysis of monoclonal antibodies using polyacrylamide gel electrophoresis, two hydrolytic fragments derived from the heavy chain of mouse IgG1 were produced during incubation of the antibodies in Laemmli reducing sample buffer at 100 degrees C for 5 min. The cleavage sites were identified by amino terminal sequencing. Results indicate that the final pH of the mixture is critical for the production of the fragments which are generated when the pH is approximately 6.0. At pH 8.0, no fragments are detected. The relevance of this finding to those working with monoclonal antibodies is discussed.

Acids↗
PubMed1992

A prospective evaluation of plasma-TFE and expanded PTFE grafts for routine and early use as vascular access during hemodialysis.

The use of prosthetic grafts as vascular access for chronic hemodialysis is frequently necessary in patients with end-stage renal disease. Most commonly, expanded polytetrafluoroethylene (e-PTFE) has been employed because of ease of handling, tissue inertness, and acceptable long-term patency. Delay in use to allow for tissue ingrowth, however, has often required placement of temporary access devices. The authors have undertaken evaluation of a new material, plasma polymerized woven dacron Plasma-TFE, in a prospective randomized trial (Plasma-TFE VA) to compare clinical behavior against e-PTFE grafts, and we have used the Plasma-TFE grafts in an additional group of patients (Plasma-TFE AVA) as early access (within 1 week of implantation). Twenty-one Plasma-TFE grafts were implanted in 19 patients and 19 e-PTFE grafts were implanted in 17 patients in a prospective randomized fashion. Additionally, 31 Plasma-TFE grafts were implanted in 31 nonrandomized patients for early access. Primary patency rates in Plasma-TFE VA and e-PTFE grafts were equivalent at 12 months (0.471 and 0.556). When Plasma-TFE AVA primary patency was included (0.621), comparisons were not statistically significant (p = 0.50). Similarly, secondary patency rates among the three groups did not differ (cumulative proportion patent at 12 months: Plasma-TFE VA 0.403, e-PTFE 0.658, Plasma-TFE AVA 0.510). In considering after-revision patency after graft thrombosis, however, the Plasma-TFE grafts (both VA and AVA) performed significantly more poorly (p = 0.027) than e-PTFE grafts. Incidence of graft infection, wound infection, arm edema, hematoma from use, and occurrence of distal limb ischemia between Plasma-TFE (VA and AVA) and e-PTFE did not differ statistically. The authors conclude that Plasma-TFE compares favorably to e-PTFE with respect to primary and secondary patency and nonthrombotic complications, even with early use. Plasma-TFE does not perform as well as e-PTFE, however, after graft thrombosis.

Blood Vessel Prosthesis↗
PubMed1989

A trial of dipyridamole and aspirin in the prevention of smoking-induced changes in platelets and endothelium in men with coronary artery disease.

A random-order, double-blind crossover study compared the effects of placebo, dipyridamole and dipyridamole plus aspirin on smoking-induced changes in endothelium and platelets. Each of 12 male habitual smokers with coronary artery disease was given dipyridamole (75 mg) and aspirin (324 mg), dipyridamole (75 mg) and placebo for aspirin, or a placebo for each drug 3 times daily for 1 week before each of three 20-minute periods (separated by 2 weeks) of smoking 2 cigarettes after a 12-hour period of abstinence. During each period of smoking there were increases in the mean values of the plasma concentrations of beta-thromboglobulin, platelet factor 4 and nicotine, the endothelial cell count and the blood level of carboxyhemoglobin. In addition, the mean platelet aggregate ratio decreased during each period. After administration of placebos for both dipyridamole and aspirin, the respective mean values +/- standard deviations before and after smoking were 28 +/- 8 and 30 +/- 7 ng/ml (beta-thromboglobulin), 7.4 +/- 1.0 and 8.2 +/- 1.4 ng/ml (platelet factor 4), 3.7 +/- 0.6 and 15.7 +/- 3.5 ng/ml (nicotine), 4.2 +/- 1.4 and 5.4 +/- 1.7/counting chamber (endothelial cell count), 5.0 +/- 2.2 and 6.6 +/- 2.2% (carboxyhemoglobin) and 0.80 +/- 0.07 and 0.68 +/- 0.10 (platelet aggregate ratio). Each of the differences between the means before and after smoking was statistically significant (p less than or equal to 0.02). Neither dipyridamole alone nor in combination with aspiring significantly affected the mean smoking-induced change in any of these variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Passive smoking affects endothelium and platelets.

Blood was obtained before and after ten healthy male nonsmokers sat for 20 minutes in open hospital corridors beside men who were already there smoking by their own initiative. Mean values before and after passive smoking were 0.87 and 0.78 for the platelet aggregate ratio, 2.8 and 3.7 per counting chamber for the endothelial cell count, 0 and 2.8 ng/mL for the plasma nicotine concentration, and 0.9% and 1.3% for the carboxyhemoglobin level. No variable changed significantly during control periods in which the subjects sat in a room where smoking was prohibited. Passive exposure to tobacco smoke affected the endothelial cell count and platelet aggregate ratio in a manner similar to that previously observed with active smoking.

Adult↗
PubMed1988

Intraseason changes in the body composition of collegiate female gymnasts.

Body composition measures were collected pre-, mid- and post-season on a team of eight national-calibre collegiate women gymnasts to examine intraseason changes. Also analysed were interseason changes using pre- and post-season data on five of the eight subjects during the current and previous year, according to a 2 x 2 (years x tests) analysis of variance repeated-measures design. Skinfold, circumference and diameter measures were collected with percentage body fat, lean body mass and body density determined by regression equations developed specifically for collegiate female gymnasts. Intraseason body weight decreased significantly from pre- to mid-season (means = 55.0 and 53.6 kg respectively); but the difference between mid- and post-season (53.9 kg) values was not significant (P greater than 0.05). The majority of the 1.4 kg weight loss occurred during intense pre-season conditioning and not during the actual season. Percentage body fat, on the other hand, decreased significantly from pre- to mid-season and mid- to post-season (means = 21.4%, 17.4% and 13.45% respectively; P less than 0.0005). Body density increased significantly from pre- to mid-season and mid- to post-season (means = 1.0476, 1.0584 and 1.0681 respectively; P greater than 0.0005). Of the circumference and skinfold values used in calculating percentage body fat and body density, only the skinfold values displayed significant decreases throughout the season. Interseason analyses revealed no significant changes in any of the dependent measures between seasons, despite consistent trends. There were no significant years x tests interactions and all intraseason changes for two seasons (n = 5) were the same as those found in more detailed analysis of a single season (n = 8) except in the case of weight loss, which was marginally significant (P less than 0.046) in the single-season and not in the dual-season analysis (P greater than 0.05). Body composition of these gymnasts changed in many ways within competitive seasons. The most pronounced changes observed were decreases in subcutaneous fat and increases in body density. This study reinforces the need for administrators, coaches and athletes to be concerned with percentage body fat and skinfold measures rather than weight alone when determining if a person is 'fat'.

Adipose Tissue↗
PubMed1987

Lack of effect of aspirin on cigarette smoke-induced increase in circulating endothelial cells.

A random-order, double-blind crossover study was done to compare the effects of placebo and two different doses of aspirin on the endothelial cell count of venous blood before and after smoking. Each of 17 male habitual smokers with coronary artery disease smoked two cigarettes during each of three 20-min periods separated by 2 weeks. Each patient was asked to take a tablet containing 150 mg of aspirin, 300 mg of aspirin or a placebo 12 h before each experimental smoking period and to abstain from smoking in the interim. Endothelial cell counts were determined by means of differential centrifugation and phase-contrast microscopy and nicotine by gas chromatography. After ingestion of placebo, the mean endothelial cell counts (+/- SD) were 2.7 +/- 0.8 and 4.5 +/- 0.9 per counting chamber before and after smoking respectively (p less than 0.001). Endothelial cell counts and plasma nicotine concentrations were not significantly correlated. Neither the mean presmoking values nor smoking-induced changes in either variable were affected either dose of aspirin. The data suggest that smoking caused acute endothelial cell desquamation which was not prevented by aspirin.

Adult↗
PubMed1986

Living-related kidney donors: a multicenter study of donor education, socioeconomic adjustment, and rehabilitation.

To determine the consequences of living-related kidney donation, a study was conducted of 536 donors whose nephrectomies had been performed at nine geographically dispersed centers during the past 12 years. The data demonstrated that greater than 84.0% of the donors thought they had been adequately informed regarding all aspects of donation, and less than 15.0% reported being pressured in their decision. Only two serious medical complications were directly attributable to the surgery, greater than 92.0% of the donors believed their health had not been adversely affected by donation, and 96.8% reaffirmed their decision regardless of the graft's success or the financial distress they experienced (P greater than .05). However, greater than 14.0% experienced direct pressure, particularly not to donate. Donation also appeared to stress previously troubled marriages, especially among donors without a religious affiliation, who were pressured to donate by their families, or who borrowed from family members (P less than .05). Substantial unreimbursed expenses (greater than or equal to $1,000) were incurred by 43 donors, and 23.2% of all donors reported that donation caused a financial hardship.

Adolescent↗
PubMed1986

Smoking-induced changes in endothelium and platelets are not affected by hydroxyethylrutosides.

A random-order, double-blind crossover study was carried out to compare the effects of placebo and hydroxyethylrutosides on the endothelial cell count, platelet aggregate ratio and plasma concentrations of beta-thromboglobulin and platelet factor 4 in venous blood before and after smoking. Each of 24 male habitual smokers and 22 male non-smokers smoked two cigarettes during each of two 20 min periods separated by 1 week. The subjects were asked to take 600 mg of o-(beta-hydroxyethyl)-rutosides (Venoruton) or a placebo four times before each experimental smoking period and to abstain from smoking for 12 h before each period. Blood was obtained just before and after experimental smoking. The mean endothelial cell count and beta-thromboglobulin concentration increased and platelet aggregate ratio decreased to a statistically significant extent after taking placebo or rutosides while the platelet factor 4 concentration did not change significantly on either occasion. Plasma nicotine concentrations were not significantly correlated with the other variables after smoking. Neither the mean presmoking values nor smoking-induced changes in any variable were significantly affected by rutosides. The data suggest that smoking caused acute endothelial cell desquamation and enhanced platelet function which were not prevented by rutosides.

Adult↗
PubMed1985

Effects of tobacco and non-tobacco cigarette smoking on endothelium and platelets.

Endothelial damage and platelet activation may mediate increased cardiovascular morbidity and mortality in tobacco cigarette smokers. Our study was designed to determine whether acute effects of tobacco smoking on endothelium and platelets could be avoided by the substitution of non-tobacco cigarettes. Twenty healthy nonsmokers smoked two tobacco cigarettes in 20 minutes and on another occasion (separated by 1 week) smoked two cigarettes made from wheat, cocoa, and citrus plants. Mean endothelial cell counts from venous blood before and after smoking tobacco cigarettes were 2.3 and 4.8 and before and after smoking non-tobacco cigarettes counts were 2.5 and 3.0. Mean platelet aggregate ratios before and after smoking tobacco cigarettes were 0.80 and 0.65 and before and after smoking non-tobacco cigarettes they were 0.81 and 0.78. Much greater effects of tobacco smoking on endothelial cell counts and platelet aggregate ratios suggest the possibility that non-tobacco cigarette smoking may be less harmful to the cardiovascular system than is tobacco cigarette smoking.

Adult↗
PubMed1985

Cigarette smoking--induced enhancement of platelet function: lack of prevention by aspirin in men with coronary artery disease.

Increased cardiovascular morbidity and mortality among cigarette smokers may be mediated in part by enhanced platelet function. Previous data showed that cigarette smoking--induced lowering of the platelet aggregate ratio of normal individuals was prevented by taking aspirin before smoking. Our study was undertaken to determine whether similar results would occur in men with coronary artery disease and whether platelet factor 4 would be released. A random-order, double-blind crossover study comparing the effects of placebo, 0.15 gm aspirin, and 0.30 gm aspirin was done in 30 male habitual smokers with coronary artery disease. Each man took a tablet containing placebo or aspirin and then abstained from smoking for 12 hours before each of three 20-minute periods of smoking two tobacco cigarettes. Immediately before and after smoking, the platelet aggregate ratio and the concentration of platelet factor 4 in platelet-poor plasma were determined from antecubital venous blood. Twelve hours after placebo, the geometric mean concentration of platelet factor 4 was 13.6 ng/ml before and 19.7 ng/ml after smoking (P = 0.0006). The mean platelet aggregate ratio was 0.77 and 0.72, respectively (P less than 0.00001). Neither dose of aspirin affected the presmoking value of or the smoking-induced change in either variable. The data indicate that smoking stimulated platelet aggregate formation and release of the contents of platelet alpha-granules, which were unaffected by preadministration of aspirin. This contrasts with the previous study of normal habitual smokers whose ingestion of 0.32 gm aspirin prevented a smoking-induced decrease in the platelet aggregate ratio.

Adult↗
PubMed1979

Y-grafts and sequential grafts in coronary bypass surgery: a critical evaluation of patency rates.

In a series of 584 patients undergoing coronary bypass, 425 patients received Y-grafts, sequential grafts, or a combination of the two. The saphenous veins from the legs frequently had Y- or double Y-branches suitable for bypasses. As many as 5 grafts have been served satisfactorily by a single proximal anastomosis. Simultaneous procedures included 45 left ventricular aneurysmectomies, 18 valve replacements, 7 carotid endarterectomies, repairs of a ventricular septal defect, an acute dissection, and coronary arteriovenous fistulas, with a total surgical mortality of 6 (1.4%). Restudy to determine graft patency was undertaken only in the 59 patients with unsatisfactory surgical results. These patients represent the worst 10% of the series in terms of surgical results. The patency rate for proximal anastomoses was 93%; Y-branchings, 93%; distal end-to-side anastomoses, 89%; and distal side-to-side anastomoses, 89%. Fifty-eight patients (98%) had at least 1 patient graft, and in 47 patients (80%) all anastomoses were patent up to six years after operation. Six patients underwent reoperation without any deaths.

Coronary Artery Bypass↗
PubMed1978

Blood loss and bank blood requirement in coronary bypass surgery.

With the use of nonblood prime and refinement in perfusion and surgical techniques, blood requirement for coronary bypass operations has been reduced to a minimum. Of 240 patients (average number of bypasses, 3.07; average pump time, two hours and 22 minutes), no blood was used in pump prime or before perfusion. During perfusion, 29 patients (12%) received 34 units of blood in the pump-oxygenator, and after bypass 64 patients (27%) received 65 units of blood in the operating room (average intraoperative use, 203 ml per patient). For the total hospital stay, the blood requirement was 728 ml per patient. For the last 60 patients operated on, the figure was 328 ml. There were no surgical deaths, and only 1 reexploration for postoperative hemorrhage (0.4%). Discharge hemoglobin level averaged 11.8 gm, whereas the admission hemoglobin level had averaged 13.8 gm. Autotransfusion, avoidance of entry into the pleural space, shorter perfusion time, postoperative platelet count of more than 150,000, and normal partial thromboplastin time tend to reduce blood requirement, but not to a striking degree. Bank blood requirement for the coronary bypass program accounted for 3.7% of the hospital need and 2% of the community need.

Adult↗