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Biomedical subjects

R S Greco

Publications and source records attributed to R S Greco.

At least 73 records · Page 4Linked to original sources
PubMed1982

Prevention of vascular prosthetic infection by a benzalkonium-oxacillin bonded polytetrafluoroethylene graft.

Polytetrafluoroethylene grafts were bonded to oxacillin using benzalkonium chloride. Grafts were then placed in the infrarenal aorta of dogs and contaminated with Staphylococcus aureus. At death or sacrifice, bonded grafts were significantly superior to that for controls in the absence of bacteria histologically, negative cultures, patency and survival. Histologic evaluation of grafts by light and electron microscopy demonstrated normal healing and neointima formation of bonded grafts. The future role of antibiotic bonding in the prevention of vascular prosthetic infections is discussed.

Animals↗
PubMed1982

Antibiotic bonding to polytetrafluoroethylene with tridodecylmethylammonium chloride.

Polytetrafluoroethylene (PTFE) treated with the cationic surfactant, triodecylmethylammonium chloride (TDMAC), binds 14C-penicillin (1.5 to 2 mg antibiotic/cm graft), whereas untreated PTFE or PTFE treated with anionic detergents shows little binding of antibiotic. TDMAC-treated PTFE concomitantly binds penicillin and heparin, generating a surface that potentially can resist both infection and thrombosis. The retention of these biologically active molecules is not due to passive entrapment in the PTFE but reflects an ionic interaction between the anionic ligands and surface-bound TDMAC. Penicillin bound to PTFE is not removed by exhaustive washing in aqueous buffers but is slowly released in the presence of plasma or when the PTFE is placed in a muscle pouch in the rat. Muscle tissue adjacent to the treated PTFE shows elevated levels of antibiotic following implantation. PTFE treated with TDMAC and placed in a muscle pouch binds 14C-penicillin when it is locally irrigated with antibiotic or when penicillin is administered intravenously. Thus, the TDMAC surface treated either in vitro or in vivo with penicillin provides an effective in situ source for the timed release of antibiotic.

Animals↗
PubMed1981

The antigenicity of synchronous cancers of the colon and rectum.

Immuno-reactivity to tumor extracts in patients with colorectal cancer was evaluated by the direct leukocyte migration inhibition assay. Hypertonic potassium chloride extracts were prepared from a group of synchronous colorectal cancers and from single colorectal cancers. Both groups of extracts were tested in patients with single colorectal cancers. All patients were tested preoperatively, none were previously treated, and none had distant metastases. Synchronous extracts showed no significant migration inhibition in allogeneic assays. Single colorectal cancers showed highly significant inhibition to autologous extracts only and not to allogeneic extracts. These data support the contention colorectal cancers are antigenically dissimilar.

Aged↗
PubMed1981

The noncovalent bonding of antibiotics to a polytetrafluoroethylene-benzalkonium graft.

This study evaluates the noncovalent bonding of anionic antibiotics to polytetrafluoroethylene grafts using benzalkonium chloride as a cationic anchor. The binding of radiolabeled surfactants and antibiotics was evaluated by liquid scintillation and in an in vitro microbiologic assay against Staphylococcus aureus. Significant quantities of antibiotic were bound when the grafts were pretreated with benzalkonium in ethanol or aqueous solution at elevated temperature. Bound antibiotic is stable in aqueous salt solutions, but slowly dissociates in the presence of blood or serum. The ionic nature of the bonding process is clarified by the use of a variety of antibiotics and surfactants with complementary charges. The ability of the benzalkonium treated grafts to adsorb antibiotic from blood is, likewise, demonstrated and the possibility of concomitantly binding heparin and antibiotic simultaneously is evaluated. These studies support the ability to noncovalently bond antibiotics to polytetrafluoroethylene surfaces and form the basis of eventually utilizing these surfaces in the prevention of vascular prosthetic infections.

Benzalkonium Compounds↗
PubMed1981

Diffusion of antibiotics from a polytetrafluoroethylene-benzalkonium surface.

The ability to bond antibiotics non-covalently to polytetrafluoroethylene surfaces was evaluated in an animal model. Grafts soaked or bonded in (14)C-penicillin were placed in subcutaneous pockets in rats and harvested at various time intervals. The amount of antibiotic present on grafts and in local tissue were evaluated by liquid scintillation counting. Antibiotic bonding resulted in higher concentrations of antibiotic present on the graft at implantation. Diffusion of antibiotics from the graft into surrounding tissues was also slowed by the bonding process. However, all grafts retained minimal activity at the end of 24 hours. The possibility of managing vascular prostheses with antibiotic bonding and local antibiotic irrigation is raised.

Adsorption↗
PubMed1981

Protection against pneumococcal bacteremia by partial splenectomy.

An animal model of partial splenectomy and its effect upon subsequent challenge with pneumococcus were evaluated. Results of these studies support the contention that partial splenectomy protects the host against pneumococcal bacteremia. The data show that small splenic remnant attached to identifiable blood vessels afford protection against sepsis. Thus, partial splenectomy may be used in massive splenic fractures if hemostasis can be achieved, even if less than 25 per cent of the spleen remains in continuity with its vascular supply. The conclusion that the filtering effect of the spleen is paramount in protecting against sepsis appears justified.

Animals↗
PubMed1980

Regeneration of the spleen after ectopic implantation and partial splenectomy.

Overwhelming postsplenectomy infection is a well-defined clinical entity resulting from the inability of the splenectomized host to combat infections with encapsulated bacteria. Because of this lethal complication, a number of alternatives to splenectomy have been studied, including autotransplantation of the removed spleen or partial splenectomy. The ability of the splenic tissue to regenerate depends on the type of procedure selected. In this study, the regenerating capacity of the splenic tissue is studied in 99 Sprague-Dawley rats. These animals were subjected to surgical autotransplantation and partial splenectomy. Our results demonstrated the superiority of partial splenectomy over autotransplantation in terms of regeneration of the splenic mass.

Animals↗
PubMed1980

Effect of an intravenous fat preparation on canine gastric secretion.

The effect of intravenous administration of a fat emulsion on canine gastric secretion stimulated by intravenous infusion of amino acids, pentagastrin or insulin was studied. The fat preparation was given at a rate of 30 ml/hour for 2 hours, and its effects were compared with those of a comparable amount of saline solution, each given on three separate occasions in each dog. Fat did not alter the Heidenhain pouch secretion stimulated by intravenous amino acids (1.10 versus 1.11 mmol of hydrogen ion, p greater than 0.9) or the gastrostomy secretion stimulated by intravenous insulin (9.22 versus 9.54 mmol of hydrogen ion, p greater than 0.7) but had a modest inhibitory effect on Heidenhain pouch secretion stimulated by pentagastrin (2.75 versus 3.54 mmol of hydrogen ion, p less than 0.05). These data provide indirect support for the contention that the inhibition of gastric secretion by fat in the gut is mediated by the release of an enterogastrone rather than by a direct effect of absorbed fat. Because gastric stimulation by intravenous fat was not observed in the dog, it seems likely that intravenous fat emulsion can be given to seriously ill patients without fear of an increased likelihood of peptic ulceration due to induced gastric hypersecretion.

Amino Acids↗
PubMed1980

Alleviation of constipation in the elderly by dietary fiber supplementation.

To alleviate the constipation problem among the elderly residents of Essex County Geriatric Center, New Jersey, a fiber-supplemented dietary regimen was started. Under this regimen, bran was added to the hot breakfast cereal, thus increasing the crude fiber content of the diet to 6-8 gm compared with the former 4-6 gm. As estimated from recent analysis data, the total dietary fiber was increased from 25 to 40 percent by the addition of bran. This amount of fiber proved effective in preventing constipation in 60 percent of the residents even though many of them had previously required laxatives. Additional programs of dietary fiber supplementation were devised for residents who did not respond to the cereal supplementation or who required nasogastric feedings. In the year following initiation of the program at this Center, the use of laxatives was virtually eliminated, and the institution's pharmacy reported a saving of $44,000 in expenditures for laxative drugs. Recipes are included for the bran-supplemented hot cereal, a special fiber-prune juice supplement, and a fiber-rich liquid for tube-feedings.

Aged↗
PubMed1980

A comparison of cellular immunity in patients undergoing electrocoagulation and resection for adenocarcinoma of the rectum.

Leukocyte migration inhibition assays in patients with carcinoma of the colon and rectum were evaluated in patients treated by electrocoagulation, abdominoperineal resection or low anterior resection and those with Duke's A and B lesions. Assays were performed before treatment, immediately after treatment and two to four months later. No statistically significant differences in cell mediated immunity, measured by leukocyte migration inhibition, were noted between those in the electrocoagulated group and those undergoing resection. However, electrocoagulation does appear to cure some carcinomas of the rectum and does afford a superior quality of survival. It is, however, associated with a higher recurrence rate than resection. Therefore, the decision to use electrocoagulation should not be based upon its effect on immune parameters. Rather, the choice between electrocoagulation, local resection and abdominoperineal resectin is based upon clinical judgment in which the risk of recurrence or metastases must be weighed against a superior quality of survival.

Adenocarcinoma↗
PubMed1979

Relation between immunity and survival in carcinoma of the colon and rectum.

Twenty-two patients with cancer of the colon and rectum were evaluated before and after surgical treatment by leukocyte migration inhibition assays using autologous and allogeneic tumor extracts. All patients were resected for cure. Patients with cancer of the colon demonstrated significant migration inhibition against autologous extracts before surgery and in the immediate postoperative period. Patients with rectal cancer did not demonstrate significant migration inhibition at any time. The possibility that immunity plays a role in the poorer prognosis of patients with rectal cancer is discussed.

Aged↗