Cephalosporin and aminoglycoside concentrations in peritoneal capsular fluid in rabbits.
To study the penetration of antibiotics into peritoneal tissue fluid, a subcutaneous tissue capsule model was modified by implanting multiple, perforated spherical capsules in the peritoneal cavity of rabbits. Capsules became vascularized, encased in connective tissue, and filled with fluid having a mean protein concentration of 3.6 g/100 ml. Capsular fluid was obtained by percutaneous needle aspiration and assayed for antibiotic by the disk plate bioassay technique. Cephalosporins were administered intramuscularly at a dose of 30 mg/kg. Mean peak concentrations of cephaloridine and cefazolin were significantly higher than cephalothin and cephapirin in capsular fluids, but the percent penetration (ratio of capsular mean peak to serum mean peak) ranged from 8.7 to 16.9% and was not significantly different among the cephalosporins. At 24 h the capsular concentration of cefazolin was significantly greater than for the other cephalosporins (P < 0.001). Lower rabbit serum protein binding observed at high in vivo concentrations may have enabled cefazolin to penetrate capsular fluid, but in vitro protein binding studies did not confirm a decrease in serum protein binding at high concentrations within the clinical range. Kanamycin and amikacin showed comparable capsular fluid peak concentrations as did gentamicin and tobramycin. The percent penetration ranged from 15.2 to 34.5% for the aminoglycosides. The only statistical difference was that amikacin penetration was significantly higher than that for tobramycin. Mean capsular concentrations of amikacin, cefazolin, and cephaloridine compared most favorably with the minimum inhibitory concentration of gram-negative bacilli at the dosages used in this study. (+info)
A cortisol suppression dose-response comparison of budesonide in controlled ileal release capsules with prednisolone.
AIM: To assess the systemic effect of oral budesonide, given as Entocort controlled ileal release capsules, over a dose range of 3-15 mg/day, compared with that of a moderate dose (20 mg/day) of prednisolone. METHODS: Twenty four healthy subjects were given 3, 9 or 15 mg budesonide or 20 mg prednisolone once daily, or 4.5 mg budesonide b.d., or placebo for 5 days in a randomized, double-blind crossover study. The area under the curve (AUC) of plasma cortisol concentration and the amount of cortisol excreted in the urine were monitored. RESULTS: Both plasma and urine cortisol suppression showed a dose-response for the daily doses of budesonide. Prednisolone, 20 mg, suppressed plasma cortisol (AUC) statistically significantly more than 15 mg budesonide (P = 0.014), and 3 mg budesonide statistically significantly more than placebo (P = 0.010). No difference in AUC was detected between 9 mg and 4.5 mg budesonide b.d. Similar results for budesonide vs. placebo were obtained from urine cortisol excretion data. However, prednisolone affected urine cortisol less than it affected plasma cortisol. CONCLUSION: After 5 days of administration, budesonide controlled ileal release capsules, in both clinical (9 mg/day) and high doses (15 mg/day), affected plasma cortisol less than a moderate (20 mg/day) dose of prednisolone. (+info)
Breast milk immune factors in Bangladeshi women supplemented postpartum with retinol or beta-carotene.
BACKGROUND: Vitamin A supplementation of mothers postpartum may improve infant health, not only by increasing vitamin A delivery to the infant through breast milk but also by increasing delivery of milk immune factors. Our hypothesis was that postpartum supplementation with vitamin A increases milk concentrations of certain soluble immune factors. DESIGN: In a double-blind trial conducted in Matlab, Bangladesh, women at 1-3 wk postpartum were randomly assigned to receive until 9 mo postpartum 1) a single dose of 60 mg retinol as retinyl palmitate followed by daily placebos (n = 69), 2) daily doses of 7.6 mg beta-carotene (n = 72), or 3) daily placebos (n = 71). Milk samples collected at baseline and 3 mo postpartum were analyzed by enzyme-linked immunosorbent assay for secretory immunoglobulin A, lactoferrin, lysozyme, and interleukin 8; by HPLC for total retinol; and by atomic absorption spectroscopy for sodium and potassium. RESULTS: After mammary epithelial permeability (defined as an elevated Na:K) and baseline immune factor concentrations were controlled for, there were no significant treatment effects on immune factors at 3 mo. Increased mammary permeability was common (25% of women at baseline and 12% at 3 mo) and was associated with higher concentrations of milk immune factors. Low body vitamin A stores at baseline, as assessed by the modified-relative-dose-response test, were associated with a higher Na:K, but neither retinol nor beta-carotene supplementation affected the prevalence of increased mammary permeability. CONCLUSIONS: Postpartum vitamin A supplementation does not increase milk concentrations of immune factors. The causes of increased mammary epithelial permeability in this population require further study. (+info)
Continuous delivery of human and mouse erythropoietin in mice by genetically engineered polymer encapsulated myoblasts.
The transplantation of polymer encapsulated myoblasts genetically engineered to secrete erythropoietin (Epo) may obviate the need for repeated parenteral administration of recombinant Epo as a treatment for chronic renal failure, cancer or AIDS-associated anemia. To explore this possibility, the human and mouse Epo cDNAs under the control of the housekeeping mouse PGK-1 promoter were transfected into mouse C2C12 myoblasts, which can be terminally differentiated upon exposure to low serum-containing media. Pools releasing 150 IU human Epo per 10(6) cells per day and 390 IU mouse Epo per 10(6) cells per day were selected. Polyether-sulfone (PES) capsules loaded with approximately 200,000 transfected myoblasts from these pools were implanted on the dorsal flank of DBA/2J, C3H and C57BL/6 mice. With human Epo secreting capsules, only a transient increase in the hematocrit occurred in DBA/2J mice, whereas no significant response was detected in C3H or C57BL/6 mice. On the contrary, all mice implanted with capsules releasing mouse Epo increased their hematocrit over 85% as early as 7 days after implantation and sustained these levels for at least 80 days. All retrieved implants released Epo and contained well preserved myoblasts. Moreover most capsules were surrounded by a neovascularization. Mice transplanted with nonencapsulated C2C12 cells releasing mouse Epo showed only a transitory elevation of their hematocrit reflecting the poor engraftment of injected myoblasts. These results indicate that polymer encapsulation of genetically engineered myoblasts is a promising approach for the long-term delivery of bioactive molecules, allowing the resolution of the shortcomings of free myoblast transfer. (+info)
Targeted chemotherapy by intratumour injection of encapsulated cells engineered to produce CYP2B1, an ifosfamide activating cytochrome P450.
The prognosis of pancreatic adenocarcinoma is poor and current treatment ineffective. A novel treatment strategy is described here using a mouse model system for pancreatic cancer. Cells that have been genetically modified to express the cytochrome P450 2B1 enzyme are encapsulated in cellulose sulphate and implanted into pre-established tumours derived from human pancreatic cells. Cytochrome P450 2B1 converts the chemotherapeutic agent ifosfamide to toxic metabolites. Administration of ifosfamide to tumour-bearing mice that were recipients of implanted encapsulated cells results in partial or even complete tumour ablation. These results suggest that in situ chemotherapy with genetically modified cells in an immunoprotected environment may prove useful for application in man. (+info)
Comparison of antiplatelet activity of microencapsulated aspirin 162.5 Mg (Caspac XL), with enteric coated aspirin 75 mg and 150 mg in patients with atherosclerosis.
AIMS: A new formulation, low dose microencapsulated aspirin, permits slow absorption of aspirin and presystemic acetylation of platelet cyclo-oxygenase within the portal circulation, potentially avoiding deleterious effects on gastric and systemic prostaglandin synthesis. The objective of this study was to determine whether the administration of microencapsulated aspirin was as effective as enteric coated (EC) aspirin as an inhibitor of platelet function in patients with atherosclerosis. METHODS: One hundred and four patients were enrolled and randomised after a run in period of at least 14 days on aspirin EC 75 mg (day 0), to receive either microencapsulated aspirin 162.5 mg (n=34), aspirin EC 150 mg (n=36) or continue on aspirin EC 75 mg (n=34) for 28 days. Serum thromboxane B2 and collagen-induced platelet aggregation and release of 5-hydroxytryptamine (EC50 values) were measured on days 0 and 28. Aggregation/release EC50s were then repeated in the presence of a large dose of aspirin added in vitro to determine the EC50 at the maximum level of platelet inhibition. RESULTS: Median thromboxane B2 levels were low after 14 days run-in therapy with aspirin EC 75 mg, but significant further reductions were seen on day 28 in patients randomised to microencapsulated aspirin 162.5 mg (P=0.0368) and aspirin EC 150 mg (P=0.0004) compared with those remaining on aspirin EC 75 mg. Median EC50 s on day 28 showed small but significant increases from baseline (day 0) in aggregation in patients randomised to microencapsulated aspirin 162.5 mg (0.62-0.85, P=0.0482) and in both aggregation and release in patients randomised to aspirin EC 150 mg (0.95-1.20, P=0.0002, 8.4-11.7, P<0. 0001, respectively) signifying enhanced antiplatelet activity. No changes were seen in patients continuing on aspirin EC 75 mg. Results following addition of high dose aspirin in vitro suggest that mechanisms other than thromboxane synthesis may be operative in the long term effects of microencapsulated aspirin 162.5 mg and aspirin EC 150 mg over aspirin EC 75 mg. CONCLUSIONS: The results show good inhibition of thromboxane B2 synthesis and subsequent platelet activity by all preparations of aspirin, although both microencapsulated aspirin 162.5 mg and aspirin EC 150 mg are slightly more effective than aspirin EC 75 mg. A randomised trial is now required to determine whether microencapsulated aspirin is associated with fewer gastric side-effects. (+info)
Improvement of mouse beta-thalassemia upon erythropoietin delivery by encapsulated myoblasts.
The goal of the present study was to analyze if sustained delivery of elevated doses of recombinant erythropoietin (Epo), by genetically modified and immunoprotected allogenic cells, was able to correct the chronic anemia, characteristic of a spontaneous mouse model of beta-thalassemia (Hbb thal 1). Mouse C2C12 myoblast cells were transfected with a plasmid containing the mouse Epo cDNA and a mutated dihydrofolate reductase (DHFR) gene for gene amplification upon administration of increasing doses of methotrexate. In order to immunoprotect the transplanted cells, the stably modified cells were loaded into polyethersulfone microporus hollow fibers which were implanted subcutaneously into Hbb thal 1 mice. An increase in hematocrit starting 2 weeks after implantation was associated with elevated blood levels of Epo and an improved red blood cell phenotype. The latter indicated an improvement of cell morphology and membrane defects, in particular a reduced amount of free alpha hemoglobin chain, the hallmark of globin chain imbalance in beta-thalassemia. A reduction of reticulocyte count contrasting with the increase in hematocrit was also observed suggesting an improved erythrocyte survival. We conclude that the phenotype can be durably improved in some beta-thalassemic mice upon in vivo delivery of recombinant Epo by polymer encapsulated cells. Sustained elevated delivery of recombinant Epo holds promise for the treatment of beta-thalassemia-associated chronic anemia. (+info)
Stabilized plasmid-lipid particles: construction and characterization.
A detergent dialysis procedure is described which allows encapsulation of plasmid DNA within a lipid envelope, where the resulting particle is stabilized in aqueous media by the presence of a poly(ethyleneglycol) (PEG) coating. These 'stabilized plasmid-lipid particles' (SPLP) exhibit an average size of 70 nm in diameter, contain one plasmid per particle and fully protect the encapsulated plasmid from digestion by serum nucleases and E. coli DNase I. Encapsulation is a sensitive function of cationic lipid content, with maximum entrapment observed at dioleoyldimethylammonium chloride (DODAC) contents of 5 to 10 mol%. The formulation process results in plasmid-trapping efficiencies of up to 70% and permits inclusion of 'fusigenic' lipids such as dioleoylphosphatidylethanolamine (DOPE). The in vitro transfection capabilities of SPLP are demonstrated to be strongly dependent on the length of the acyl chain contained in the ceramide group used to anchor the PEG polymer to the surface of the SPLP. Shorter acyl chain lengths result in a PEG coating which can dissociate from the SPLP surface, transforming the SPLP from a stable particle to a transfection-competent entity. It is suggested that SPLP may have utility as systemic gene delivery systems for gene therapy protocols. (+info)